Acid generator and thin film composition containing the same

ABSTRACT

The present invention relates to the compounds generating strong acids (described hereafter as “acid generators”) decomposed by heat and the composition of thin film containing the same. Provided are the compounds represented by the structure of formula I and the composition containing the compounds.  
                 
wherein X is alkyl or aryl group and R is hydrogen atom, hydroxy, alkoxy or alkyl group. The abovementioned acid generators of the present invention generate acid by heat at relatively low temperatures, preventing the change in the ratio of the composition due to evaporation of some components in the composition. Accordingly, it has the advantageous effect that the ratio of components in the composition is controlled and the preparation of the thin film with the wanted properties is simplified.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the compounds generating strong acids(described hereafter as “acid generators”, decomposed by heat and thecomposition of thin films containing the same. Particularly, the presentinvention relates to the composition which maintains the thin filmnotwithstanding the severe condition because of the cross linkingreaction carried out by the generated acid.

2. Description of the Related Arts

In recent years, great interests are shown on the thin film as theindustrial sectors develop rapidly. The thin film technology is used inthe processes of ultra fine semiconductors as well as in the householdelectronic products and furniture. For example, an organic thin filmcomposition is used in the manufacturing process of semiconductor toshield the reflection of light from the bottom layer and to increase theadhesive strength to the substrate. In case it is not shielded,deformation in the ultra fine pattern occurs. When the substrate coatedby thin film is exposed to the ArF eximer laser, the light of 193 nmwave length is reflected by the substrate, making the patterns change.The thin film technology is utilized also in the manufacturing processof LCD, to protect the top part of the color filter and the thin film isused as a means to protect the surface of the household electronicproducts and the furniture.

The technology of making thin films is categorized into two methodsaccording to the catalyst employed. One method is the technology usingradical initiator. The frequently used resin in this case is acrylatederivatives. The functional group participating in the reaction is theunreacted acrylate. The other method is the technology using cationcatalyst in making the thin films. The resin generally used in theprocess is the acrylates derivatives containing epoxy group. The epoxygroup easily goes into cross linking reaction by strong acids.

The technology using radical initiator to make the thin films has to beblocked from oxygen in the air, making the process problematic, whilethe technology of using cation catalyst has the advantage of not needingthe oxygen blockade.

The cation catalysts are grouped into the compounds according to theircharacteristics whether generation of acid is by light or by heat. Thecompounds generating acid by light include iodonium salts, sulfoniumsalts, phosphonium salts, diazonium slats, pyridinium salts and amides.The compound generating acid by heat includessec-alkyl-p-toluenesulfonate.

The acid generators by heat or light has to possess both appropriatestability and the property of decomposing by heat according to the uses.When the acid generator decomposes easily by heat or during storageperiod, it loses the product value, while it also loses the productvalue when it is too stable to heat because it lacks in reactivity.

SUMMARY OF THE INVENTION

The present invention is to provide novel acid generators which arestable during the long storage period and under the intended temperaturein consideration of the above needs.

Other object of the present invention is to provide the compositioncontaining the abovementioned novel acid generators.

These objects of the present invention are accomplished by the novelacid generators represented by the structure of the following formula I.

-   -   wherein X is alkyl or aryl group and R is hydrogen atom, hydroxy        group, alkoxy group or alkyl group.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanying drawing,in which:

FIG. 1 is the NMR diagram of the novel acid generator of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following is the illustration of the general properties of theacid generators, exhibited by the compound of the chemical formula Iwhich is the acid generator of formula I wherein X is toluene group.

When heat or acid is added to the compound represented by the chemicalformula I, decomposition reaction occurs around 110° C. and themechanism of decomposition is as in the following reaction scheme I.

The compound of the chemical formula I is decomposed by heat into olefinand toluenesulfonic acid. The generated toluenesulfonic acid havingfunctions as a strong acid in the thin film composition. The FIG. 1 isNMR (nuclear magnetic resonance) diagram which identifies the structureof the chemical formula I.

The conventionally used sec-alkyl-p-toluenesulfonate has the higherdecomposition temperature of 150° C. Because of this high temperature,it has shortcomings in that the volatile components of the thin filmcomposition evaporate easily.

The major constituents of the thin film composition including the aboveacid generator are the compounds which have the functional groupreacting in the cross linking reaction(described hereafter as “crosslinking agent”), acid generator, resin, some additive and the solventdissolving these materials.

Cross Linking Agent

A cross linking agent is a modifier of the original property of acompound by the reaction with acid, light or radical initiator. Examplesare the compounds represented by the structure of the general formulaII, III and IV.

In the formula II, R1 and R2 both are alkyls and m/(m+n) is in the rangeof 0.3 to 0.8.

In the formula III, R3 and R4 are all hydrogen atoms or alkyl groups, R5is hydrogen atom, alkoxy group, hydroxyalkyl epoxyalkyl group,alkoxyalkyl group or hydroxy group and m′/(m′+n′) is in the range of 0.2to 1.0.

In the formula IV, R6 and R8 are hydrogen atom or methyl group, R7 ishydrogen atom, alkoxy group, hydroxyalkyl epoxyalkyl group, alkoxyalkylgroup or hydroxy group, R9 and R10 are alkyl groups and m″/(m″+n″) is inthe range of 0.2 to 1.0.

The compound represented by the formula II is the resin of acroleinpolymer, part of which is acetalized by alcohol. This compound produceshigh molecular compounds by going into cross linking reaction withalcohol or phenol under the acid catalyst.

The compound represented by the formula III is easily synthesized byusual radical reaction. The compound goes into cross linking reactionwith tetrahydrofurfuryl group. The functional group proceeds into crosslinking reaction by opening the ring under the strong acid catalysts.The cross linking reaction either proceeds alone or with alcohols orphenols.

The compound represented by the formula IV is a modified acroleinpolymer copolymerized with other monomer to improve its shortcoming ofsolubility in general solvents. This polymer and the intermediate havethe advantage of good solubility.

Acid Generator

The acid generators are grouped into two categories of generating acidby either heat or light according to molecular characteristics. Thecompounds generating acid by light include onium types such as iodoniumsalts, sulfonium salts, phosphonium salts, diazonium slats, pyridiniumsalts and amides. The other kind of compound generating acid by heatincludes sec-alkyl-p-toluenesulfonate. Acid generators either by heat orlight are used according to different kinds of thin films. It is betterto use the acid generator by light when there is the chance ofdeformation by heat. But the onium type has disadvantage of beingexpensive. In some cases, solubility of the composition decreases.

The novel acid generators of the present invention, represented by thefollowing formula I, have appropriate stability and reactivity underheat.

-   -   wherein R is hydrogen atom, hydroxy, alkoxy or alkyl group.

The characteristics of the compounds are in that they are soluble inalmost all organic solvents and have easy manufacturing process,providing low cost thin films. Another advantage is that, due to theproperty of norbomene, the compounds generate acid at a low temperature,compared with other secondary alkyl group (for example, cyclohexyl,isopropyl and cyclopentyl group). The temperature of acid generation forusual secondary alky group is at around 150° C. while that of norbomanylgroup is at around 110° C. The temperature of acid generation isimportant because at the temperature more that 130° C., the volatilecomponents such as low molecular additives, evaporate, degrading theproperties of the thin film.

The acid generators described above are synthesized by reacting olefinand epoxy compounds with alkyl sulfonic acid or aryl sulfonic acid. Thedetailed synthetic method is described in the examples of synthesis. Theschematic reaction route is illustrated in the following.

The reaction between norbornene and toluenesulfonic acid proceeds veryslowly and the temperature has to be raised to around 70° C. But thereaction with expoxide compound proceeds very rapidly at around 0° C.Both compounds are used after recrystalization in usual organic solventafter termination of the reactions. The thin films are readilymanufactured with these compounds, yet for the specific properties andspecific use of the thin film, small amount of onium types such asiodonium salts, sulfonium salts, phosphonium salt, diazonium salts,pyridinium salts and amides are added.

Resin and Additives

When the cross linking agent is resin itself, another resin is notneeded according to the use. But for the optimization of the wantedproperties, addition of another resin is required. For example for thebottom anti-reflective coating in the manufacturing process ofsemiconductor, specific compounds or resins absorbing UV light are used.In order to absorb UV light of 193 nm wave length, the resins orcompounds substituted with aromatic functional groups are used and forthe UV light of 248 nm wave length, anthracene substituted resins andcompounds are used. The resins absorbing UV light of 193 nm wave lengthare polyhydroxystyrene, polyacrylate or polystyrene.

For additives, utilized are a plasticizer for controlling the strengthof the thin film, polyhydroxy or epoxy compounds for the effectiveproceeding of the cross linking reaction, surfactant for uniformity ofthe thin film and homogenous mixing of the solution and light inducedacid generator of onium types such as iodonium salts, sulfonium salts,phosphonium salt, diazonium salts, pyridinium salts and amides when thecomposition is used for the anti-reflective layer.

For the homogeneous and smooth coating layer by the thin filmcomposition, solvents with appropriate evaporation velocity andviscosity are used to make solution. Such solvents includeethyleneglycol monmethyl ether, ethyleneglycol monoethyl ether,ethyleneglycol monopropyl ether, methylcellosolve acetate,ethylcellosolve acetate, propyleneglycol monomethyl ether acetate,propyleneglycol monoethyl ether acetate, propyleneglycol monopropylether acetate, methyl isopropyl ketone, cyclohexanone, methyl2-hydroxypropionate, ethyl 2-hydroxypropionate, 2-heptanone, ethyllactate or γ-butyrolactone. In some cases, mixtures of more than two ofthese compounds are used. The amount of solvents are controlledappropriately to have homogeneity of the solution in consideration ofthe evaporation and viscosity of the solvent.

The following examples are a detailed description of the presentinvention. The examples are presented for illustrative purposes only andare not intended as a restriction on the scope of the present invention.Synthesis 1—Synthesis of the Acid Generator Represented by the Structureof Formula I

100 g of norbornene and 100 g of toluenesulfonic acid were added into 1liter flask and dissolved in 500 ml of chloroform. The solution washeated to 70° C. and stirred for 5 hours. The solution was cooled downto room temperature and washed with aqueous Na2CO3 solution. The washedorganic layer was washed more than 2 times with distilled water and thesolvent was completely eliminated. The reaction mixture without thesolvent was dissolved in hexane and cooled down to 10° C. to obtainwhite solids. The solids were filtered and obtained 130 g of thecompound represented by formula I.Synthesis 2—Synthesis of the Polymer Represented by the Structure ofFormula II

50 g of acrolein and 100 ml of ethyl acetate were added into 250 mlflask and 6 g of AIBN was added and dissolved. The solution was heatedto 70° C. and stirred for 12 hours. The solution was cooled down to roomtemperature and the produced solids were filtered and dried. The driedsolids were put into 500 ml flask and 200 ml of methanol and 0.2 g ofsulfuric acid were added and stirred at 60° C. for 15 hours. Thesolution was cooled down to room temperature and neutralized with 0.5 mlof triethylamine. The neutralized solution was slowly dropped intoexcess distilled water to obtain while solids. The solids were filteredand dried to obtain 58 g of the polymer of the formula II with m valuearound 0.6.Synthesis 3—Synthesis of the Polymer Represented by the Structure ofFormula III

16 g of tetrahydrofurfuryl methacrylate and 5 g of acrotein weredissolved in 60 ml of isopropyl alcohol. 0.8 g of AIBN was added andheated to 70° C. The solution was stirred for 8 hour at this temperatureand cooled to room temperature. The solution was dropped slowly intoexcess distilled water. The produced solids were dried and obtained 18 gof the polymer of the formula III with m′ value around 0.7.Synthesis 4—Synthesis of the Polymer Rpresented by the Structure ofFormula IV

100 g of methylacrylate, 100 g of acrolein and 10 g AIBN were dissolvedin 400 g of dioxane and the reaction temperature was raised to 70° C.After stirring at this temperature for 15 hours, the unreacted monomerand the solvent, dioxane, were eliminated by vacuum distillation. Intothe reactor, 400 g of methanol and 1 g of sulfuric acid were added andreacted for 8 hour at the same temperature. The reactants were cooleddown to room temperature and was dropped slowly into excess amount ofdistilled water. The produced solids were dried and obtained 210 g ofthe polymer of the formula IV with m″ value of 0.4.Synthesis 5—Synthesis of the Polymer Represented by the Structure ofFormula V

50 ml of tetrahydrofurfuryl methacrylate and 33 g of methyl methacrylatewere dissolved in 100 ml of acetone. After adding 6 g or AIBN, heated to65° C. and stirred for 6 hours. The reactants were cooled down to roomtemperature, additional 300 ml of acetone was added to dissolve and thesolution was dropped slowly into excess amount of distilled water. Theproduced solids were dried and obtained 76 g of the polymer of theformula V with m′ value of 0.6.

EXAMPLE 1

0.6 g of the polymer obtained in synthesis 2, 0.1 g of the acidgenerator obtained in synthesis 1 and 0.4 g of polyhydroxystyrene weredissolved in 45 g of propyleneglycol methylether acetate and filteredwith 0.2 μm membrane filter to make the composition for the thin film.The composition was spin coated on the substrate and heated at 190° C.for 90 seconds to form the thin film (the anti-reflective film ofblocking the light of 193 nm wave length). On the thin film ArF resistwas spin coated and heated 90 seconds at 110° C. in order to formmulti-layered thin film. The substrate was exposed to light using theArF eximer laser exposure apparatus and heat treated at 130° C. for 90seconds. The substrate is cooled down and developed for 40 seconds andwashed with 2.38 wt % of aqueous tetraammonium hydroxide solution anddried to form a resist pattern. The produced resist pattern had verygood adhesive property and obtained very excellent pattern profile atthe resolution of 0.13 μm.

Comparison Example 1

ArF was spin coated on the substrate without the thin film compositionand heated at 110° C. for 90 seconds to make thin film. The substratewas exposed to light using the ArF eximer laser exposure apparatus andheat treated at 130° C. for 90 seconds. The substrate is cooled down anddeveloped for 40 seconds and washed with 2.38 wt % of aqueoustetraammonium hydroxide solution and dried to form a resist pattern. Thecompleted pattern had low adhesive property. At less than 0.15 μmpattern, the phenomenon of the patterns being detached is observed andat 0.18 μm resolution, side surface of the pattern profile is observedto be not uniform.

EXAMPLE 2

Carried out the same experiment as described In the Example 1, exceptusing 0.6 g of polymer synthesized in the Synthesis 3 instead ofSynthesis 2. The result showed excellent adhesive property of the resistpattern and excellent vertical pattern profile at 0.13 μm resolution.

EXAMPLE 3

Carried out the same experiment as described In the Example 1, exceptusing 0.6 g of polymer synthesized in the Synthesis 4 instead ofSynthesis 2. The result showed excellent adhesive property of the resistpattern and excellent vertical pattern profile at the resolution of 0.12μm.

EXAMPLE 4

Carried out the same experiment as described In the Example 1, exceptusing 0.6 g of polymer synthesized in the Synthesis 5 instead ofSynthesis 2. The result showed excellent adhesive property of the resistpattern and excellent vertical pattern profile at the resolution of 0.1μm.

EXAMPLE 5

Carried out the same experiment as described In the Example 4, exceptusing additionally 50 ppm of fluorinated ether type surfactant. Theresult showed excellent adhesive property of the resist pattern andexcellent vertical pattern profile at the resolution of 0.11 μm.

EXAMPLE 6

2 g of polymer obtained in Synthesis 5 and 0.001 g of the acid generatorobtained in Synthesis 1 were dissolved in 50 g of propyleneglycolmethylether acetate and filtered by 0.2 μm membrane filter to formulatea thin film composition. The composition was spin coated on a glasssubstrate and heated at 190° C. for 90 seconds to make the thin film.The completed thin film was homogeneous and formed a coated layer whichwas not dissolved in usual organic solvents.

EXAMPLE 7

Carried out the same experiment as described In the Example 6, exceptusing additionally 0.2 g of glycerol. The result showed that thecompleted thin film was homogeneous and it formed a coated layer whichwas not dissolved in usual organic solvents.

The abovementioned acid generator of the present invention generatesacid by heat at a relatively low temperature, preventing the change inthe ratio of the composition due to evaporation of some components inthe composition. Accordingly it has the advantageous effect that theratio of components in the composition is controlled and the preparationof the thin film with the wanted properties is simplified.

1. A composition of a thin film comprising the compound represented bythe structure of the formula I

wherein X is alkyl or aryl group and R is hydrogen atom, hydroxy group,alkoxy group or alkyl group; cross linking agent, resin, additives andsolvents.
 2. (canceled)
 3. (canceled)
 4. The composition of the thinfilm as set forth in claim 1, wherein the resin is selected more thanone from the group of polyhydroxystyrene, polystyrene and polyacrylate.5. The composition of the thin film comprising the compounds of claim 1,cross linking agent, additives and solvents.
 6. The composition of thethin film as set forth in claim 1 or claim 5, wherein the cross linkingagents is the polymer represented by the structure of formula II.

wherein R1 and R2 both are alkyl group and m/(m+n) is in the range of0.3 to 0.8.
 7. The composition of the thin film as set forth in claim 1or claim 5, wherein the cross linking agent is the polymer representedby the structure of formula III.

wherein R3 and R4 are all hydrogen atoms or alkyl groups, R5 is hydrogenatom, alkoxy group, hydroxyalkyl epoxyalkyl group, alkoxyalkyl group orhydroxy group and m′/(m′+n′) is in the range of 0.2 to 1.0.
 8. Thecomposition of the thin film as set forth in claim 1 or claim 5, whereinthe cross linking agent is the polymer represented by the structure offormula IV.

wherein R6 and R8 are hydrogen atom or methyl group, R7 is hydrogenatom, alkoxy group, hydroxyalkyl epoxyalkyl group, alkoxyalkyl orhydroxy group group, R9 and R10 are alkyl groups and m″/(m″+n″) is inthe range of 0.2 to 1.0.